Matlab image - comment compter le nombre de pixels blancs

Question

Le code matlab ci-dessous scinde une image en plusieurs petites images. Il compte ensuite le nombre de pixels noirs dans l'image et l'affiche en pourcentage du nombre total de pixels dans l'image. Ma question est - au lieu de compter les pixels noirs et d'afficher le pourcentage, comment puis-je compter les pixels blancs? (Essentiellement le contraire!)

Merci

% Divide an image up into blocks (non-overlapping tiles). 

clc; % Clear the command window. 
close all; % Close all figures (except those of imtool.) 
workspace; % Make sure the workspace panel is showing. 
fontSize = 20; 

% Read the image from disk. 
rgbImage = imread('edge-diff.jpg'); 

% Display image full screen. 
imshow(rgbImage); 


% Enlarge figure to full screen. 
set(gcf, 'units','normalized','outerposition',[0 0 1 1]); 
drawnow; 
% Get the dimensions of the image. numberOfColorBands should be = 3. 
[rows columns numberOfColorBands] = size(rgbImage) 

%========================================================================== 
% The first way to divide an image up into blocks is by using mat2cell(). 
blockSizeR = 400; % Rows in block. 
blockSizeC = 400; % Columns in block. 

% Figure out the size of each block in rows. 
% Most will be blockSizeR but there may be a remainder amount of less than that. 
wholeBlockRows = floor(rows/blockSizeR); 
blockVectorR = [blockSizeR * ones(1, wholeBlockRows), rem(rows, blockSizeR)]; 
% Figure out the size of each block in columns. 
wholeBlockCols = floor(columns/blockSizeC); 
blockVectorC = [blockSizeC * ones(1, wholeBlockCols), rem(columns, blockSizeC)]; 

% Create the cell array, ca. 
% Each cell (except for the remainder cells at the end of the image) 
% in the array contains a blockSizeR by blockSizeC by 3 color array. 
% This line is where the image is actually divided up into blocks. 
if numberOfColorBands > 1 
    % It's a color image. 
    ca = mat2cell(rgbImage, blockVectorR, blockVectorC, numberOfColorBands); 
else 
    ca = mat2cell(rgbImage, blockVectorR, blockVectorC); 
end 

percentBlack = cellfun(@(x)sum(sum(all(x == 0, 3)))/(numel(x)/size(x,3)), ca); 


% Now display all the blocks. 
plotIndex = 1; 
numPlotsR = size(ca, 1); 
numPlotsC = size(ca, 2); 
for r = 1 : numPlotsR 
    for c = 1 : numPlotsC 
     fprintf('plotindex = %d, c=%d, r=%d\n', plotIndex, c, r); 
     % Specify the location for display of the image. 
     subplot(numPlotsR, numPlotsC, plotIndex); 
     ax2 = subplot(numPlotsR, numPlotsC, plotIndex); 
     % Extract the numerical array out of the cell 
     % just for tutorial purposes. 
     rgbBlock = ca{r,c}; 
     imshow(rgbBlock); % Could call imshow(ca{r,c}) if you wanted to. 
     [rowsB columnsB numberOfColorBandsB] = size(rgbBlock); 
     set(ax2, 'box', 'on', 'Visible', 'on', 'xtick', [], 'ytick', []); 
     % Make the caption the block number. 
     averageBlack = percentBlack(r,c); 
     disp(numPlotsR); 
     disp(averageBlack); 
     caption = sprintf('Frame #%d of %d\n Percentage information content %0.2f', ... 
      plotIndex, numPlotsR*numPlotsC, averageBlack*100); 
     title(caption); 
     drawnow; 
     % Increment the subplot to the next location. 
     plotIndex = plotIndex + 1; 
    end 
end 

Answer 1

Cette ligne:

percentBlack = cellfun(@(x)sum(sum(all(x == 0, 3)))/(numel(x)/size(x,3)), ca); 

spécifiquement la partie qui dit all(x == 0, 3) signifie "tous les canaux de couleur ont une valeur 0". Vous voulez changer pour « tous les canaux de couleur ont une valeur 1 (ou 255 dépend de votre image) »

Donc, fondamentalement, changer que 0-1 ou 255, deependinf si votre image est unit8 ou double